JPH06279755A - Fluid for shielding electric field - Google Patents

Abstract

PURPOSE:To obtain the fluid which is excellent in transparency and film-forming properties and provides an electric conductivity enough to shield a leakage electric field from a cathode ray tube by dispersing a specific indium tin oxide powder and a specific binder in a specific polar solvent. CONSTITUTION:The fluid is obtd. by dispersing 1-15wt.% (based on the fluid) indium tin oxide powder having content of 1-10wt.% and an average particle size of 50nm or smaller and 0.1-6wt.% (based on the fluid) binder comprising a 1-4C alkyl silicate (e.g. orthoethoxy silicate) in a polar solvent contg. N- methylpyrrolidinone and at least one solvent selected from a group consisting of ethanol, acetone, tetrahydrofuran, isopropyl alcohol, diacetone alcohol, and dimethylformamide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment liquid for electric field shield used for electric field shield of displays of OA equipment, cathode ray tubes of televisions, etc., especially coating or spraying.
The present invention relates to an electric field shield treatment liquid suitable for an electric field shield by a spin coating method.

[0002]

2. Description of the Related Art On the surface of a television cathode ray tube,
It has been known for a long time that electric field shielding measures are taken because dust due to electrostatic charging is easily adsorbed, and when a human body comes into contact, it discharges and receives an electric shock.

In particular, due to the recent automation of office automation (OA), many OA devices have been introduced into an office, and it is not uncommon for an environment in which work is performed all day facing the display of the OA device. When working in contact with a cathode ray tube (CRT) of a computer, the display screen is easy to see, the image is easy to read, and the visual fatigue is felt, not only due to the adhesion of dust on the CRT surface due to static electricity and electric shock. In addition to not letting it leak,
The effects of the leakage electromagnetic field on the human body must clear safety standards.

Among the above requirements, the problems associated with electrostatic charging are solved by attaching a conductive film to the surface of the CRT and grounding it. However, since the CRT is the surface of a transmission image, the conductive film is transparent. It is preferable that it is excellent. In order to make the screen easier to see, it is achieved by suppressing the reflection of the screen by antiglare processing, and in order to make the image easier to read, the selection of the emission color is an important factor.

The shielding of X-rays occurs near the shadow mask, so the glass of the cathode ray tube is covered with Pb, Ba, Sr.
It suffices to add a heavy element such as to have a shielding effect. The electromagnetic field is generated around the electron gun, and a larger electromagnetic field tends to leak to the surroundings as the TV becomes larger. The magnetic field leakage can be prevented by applying a reverse magnetic field, and the countermeasure against the electric field leakage can be prevented by forming a conductive transparent film on the surface of the CRT glass as in the case of preventing the charging. But,
There is a large difference in the level of conductivity required for the coating between the electric field shield and the antistatic property, and a surface resistance of about 10 ¹¹ Ω / □ is sufficient for the antistatic property. In order to prevent this, it is necessary to form a transparent film having a low resistance of less than 10 ⁵ Ω / □.

For the antiglare treatment, the film thickness and the refractive index of the film may be controlled so that the reflected light causes destructive interference with the incident light. Therefore, if a film having a resistance value and an optical characteristic is formed, the reflectance problem is a problem to be solved by adjusting the conditions at the time of film formation.

In order to meet the above demands, various proposals have been made conventionally. Since the inside of the cathode ray tube is in a high vacuum of about 10 ⁵ Pa, it is designed to increase the wall thickness of glass or to have a curved surface shape to withstand the pressure of the atmosphere. Since it is not possible to heat the cathode ray tube in this state to a high temperature, the formation of the surface coating is substantially 200 ° C.
It must be done at the following temperatures: As a method capable of forming a film at such a low temperature, for example, vacuum deposition and CVD
There is a method of forming a film of a conductive oxide such as tin oxide or indium oxide on the front surface of the CRT.

[0008]

However, although this method can obtain a sufficiently low resistance value for the electric field shielding effect, it requires a great deal of cost to form a film, so that it is a practical CRT.
It is extremely inconvenient to manufacture, and a cheaper coating method is desired.

As an inexpensive coating method, a method of spraying or coating an ink composition is disclosed in JP-A-1-299.
No. 887. In this example, the ink consists of particulate tin oxide, silica sol and organic solvent,
The film is formed by utilizing the polymerization reaction of silica sol which can be performed at a low temperature of ℃ or less. However, this gives only conductivity satisfying the antistatic function. That is, the surface resistance of the transparent conductive film formed using this treatment liquid is at least about 10 ⁷ Ω / □, which is far below the conductivity required to shield the leakage electric field.

An object of the present invention is to provide a treatment liquid for electric field shield which is excellent in transparency and coatability, and in particular provides sufficient electric conductivity to shield a leak electric field of a cathode ray tube.

[0011]

In order to achieve the above object, the treatment liquid for electric field shield according to the present invention is a treatment liquid for electric field shield in which indium tin oxide powder and a binder are dispersed in a polar solvent. The indium tin oxide powder has a tin content of 1 to 10% by weight and an average particle size of 50 nm.
The content is 1 to 15% by weight, and the binder is an alkyl silicate in which the alkyl group is methyl, ethyl, propyl, butyl, and the content of the alkyl silicate is 0.1.
The polar solvent contains N-methyl-2pyrrolidinone and one or more of ethanol, acetone, tetrahydroxyfuran, isopropyl alcohol, diacetone alcohol and dimethylformamide.

The weight ratio of the indium tin oxide powder to the alkyl silicate is 0.1 to 0.6.

The polar solvent contains N-methyl-2pyrrolidinone and ethanol, and is N-methyl-
The content of 2 pyrrolidinone is 1 to 20% by weight, and the content of ethanol is 25 to 90% by weight.

[0014]

The indium tin oxide powder (ITO powder) having a tin content of 1 to 10% by weight and a diameter of 50 nm or less is selected as the conductive material, and the alkyl silicate is used as the binder.
-By dispersing this in a polar solvent containing methyl-2pyrrolidinone and ethanol, the transparency at the time of film formation is improved, and since ITO particles originally have lower resistance than tin oxide particles, they are low. A conductive film having a resistance value can be obtained. The dispersibility of ITO particles is 3.25 to 1 for ITO particles.
2.75% by weight, alkyl silicate 0.75-5.2
5% by weight, N-methyl-2pyrrolidinone 3.0-13.
It has the best dispersibility under the mixing ratio of 5% by weight and 25-75% by weight of ethanol, and the conductivity is improved by eliminating the bias in the conductive path, and the disturbing elements of electromagnetic wave propagation are dispersed to transmit light. Excellent optical characteristics such as a rate and a haze value can be obtained.

The content of tin in the ITO fine particles is preferably in the range of 1 to 10% by weight, particularly 1 to 6% by weight in consideration of the conductivity of ITO. The content of the ITO fine particles is 1 to 15% by weight, and particularly 3.25 to 12.75.
Weight percent is preferred. If it is less than 3.25% by weight, the smaller the content is, the thinner the film thickness is, and the connectivity of the ITO fine particles after drying is deteriorated, so that the film forming state is deteriorated and the required conductivity is obtained. I can't. Also, the content is 1
If it exceeds 2.75% by weight, as the content increases, cracks and the like are generated from the film surface and the resistance value varies.

The content of alkyl silicate is 0.1-0.1%.
6% by weight, particularly 0.75 to 5.25% by weight is preferred.
This is because if the amount is less than 0.75% by weight, the film-forming property and the film strength will decrease depending on the degree, and as the amount exceeds 5.25% by weight, the surface resistance tends to exceed the required value.

The mixing ratio of the ITO fine particles to the alkyl silicate is preferably 0.1 to 0.6 by weight,
When this ratio is less than 0.1, the film forming property becomes poor and the film strength becomes weak. Furthermore, the haze value, which is an optical characteristic, becomes high.
If it exceeds 0.6, the optical characteristics and the film strength are sufficient, but the surface resistance becomes too high, and it is not suitable for electric field shielding.

The alkyl silicate is a binder for the glass surface of a cathode ray tube or the like, and includes tetramethoxysilane, etraethoxysilane, tetrapropoxysilane,
The alkyl group such as tetrabutoxysilane may be any of methyl, ethyl, propyl and butyl, and there is no problem even if two or more kinds are mixed and used.

The content of N-methyl-2pyrrolidinone in the polar solvent is 1 to 20% by weight, particularly 3.0 to 13.5% by weight, and in the case of ethanol, acetone and tetrahydroxyfuran, it is 25 to 90% by weight. % By weight, especially 25-75
Weight% is preferable, and if it exceeds this range, the ITO fine particles tend to condense and settle, and the dispersibility deteriorates. Since the surface of the ITO particles is charged in the solvent and forms an electric double layer with the solvent, electrostatic repulsion due to adsorption of solvent molecules (or ions) near the surface of the ITO particles causes It is one of the factors that influence the dispersion / aggregation of each other. In particular, when NMP is less than 1% by weight, the absolute value of the potential difference (zeta potential) in the diffusion layer portion of the electric double layer is small, and the repulsive force between ITO particles is not sufficiently repulsive, so that the dispersion system is not stabilized, If it exceeds 20% by weight, not only the film-forming property of the entire electric field shielding treatment liquid is deteriorated but also the film strength is deteriorated, which is not preferable. Further, by preliminarily dispersing and mixing the ITO fine particles in NMP, the dispersibility of the fine particles in the electric field shielding treatment liquid can be greatly improved. When the dispersibility of ITO is poor, not only the optical characteristics are significantly deteriorated, but also the conductivity is deteriorated. Other solvents include:
Any solvent may be used as long as it is compatible with the above-mentioned solvent, for example, isopropyl alcohol, diacetone alcohol (4hydroxy-4methyl-2pentanone), dimethylformamide, etc. are used, and water, dilute hydrochloric acid or dilute nitric acid is used as a catalyst for the silicate polymerization reaction. Etc. are used.

The treatment liquid of the present invention can be formed into a film on the glass surface of a CRT by coating, spraying or spin coating.

In spin coating the glass surface of the cathode ray tube, it is desirable to preheat the glass surface to 30 to 80 ° C. This is because the seasonal difference in film production is removed, and the preheating heats the ink drying rate to an optimum value, which in particular improves the optical characteristics. The rotation speed of the spin coater is appropriately in the range of 100 to 200 rpm.
If it is 100 rpm or less, the centrifugal force for spreading the ink against the solvent viscosity is insufficient to obtain a uniform film, and if it is 200 rpm or more, the function of the cathode ray tube is damaged, which is not preferable.

[0022]

EXAMPLES Examples of the present invention will be shown below. First, an alkyl silicate solution for treating solution preparation was obtained as follows. Orthoalkyl silicate (Tama Chemical Industry) 74
While stirring a mixed solution of g, 85 g of diacetone alcohol and 7.5 g of distilled water, a mixed solution of 15 g of a 5% hydrochloric acid aqueous solution and 30 g of diacetone alcohol was added dropwise. Thus, the silicate solution was prepared.

Next, ITO fine particles (produced by Sumitomo Metal Mining Co., Ltd.)
An ITO solution was obtained by ball milling for 12 hours with a mixed solution of -methyl-2-pyrrolidinone (NMP) and ethanol. As the balls, zirconia balls having a diameter of 5 mm were used.

In the two solutions obtained as described above,
Dimethylformamide (DM to prevent film cracking during drying
F) and a diluting solvent alcohol (ethanol, isopropyl alcohol (IPA), diacetone alcohol) were added to adjust to a predetermined concentration. Table 1 shows the average particle diameter and the Sn content of the ITO fine powder used. Since no tin oxide diffraction line was observed by X-ray diffraction in all of the powders A to D, solid solution of Sn was confirmed.

The result of observation with an electron microscope showed that the particles had no aggregates. The obtained treatment liquid was formed into a film on a glass substrate for evaluation as follows. Glass substrate (2
After washing (0 × 10 cm, thickness 3 mm) with acetone,
It is put in a dryer kept at 60 ° C. and heated to a predetermined temperature. Set the heated glass substrate on the spin coater,
The solution is supplied from a beaker to form a film. After drying, 120
To 200 ° C. for 30 minutes for firing. The obtained transparent conductive film was evaluated for surface resistance, transmittance, haze and film strength. To measure the surface resistance, Mitsubishi Yuka Co., Ltd.
A surface resistance meter MCP-T200 was used. The transmittance and haze value are HR-1 manufactured by Murakami Color Research Laboratory Co., Ltd.
00 was used. The film strength was evaluated by a scratch coating hardness tester manufactured by Toyo Seiki Seisakusho.

[0026]

[Table 1] ITO fine powder ━━━━━━━━━━━━━━━━━━━━━━━━ Sample Sn content (% by weight) Average particle size (nm) ━━━━━ ━━━━━━━━━━━━━━━━━━━ A 1.3 18 B 4.3 15 C 9.1 25 D 3.3 3.3 70 ━━━━━━━━━━━━ ━━━━━━━━━━━━━

(Examples 1 to 8) The treatment liquids shown in Table 2 were prepared using the ITO fine powder B shown in Table 1 and orthoethoxysilicate as the silicate. For evaluation, the glass substrate temperature was 45 ° C. and the spin coating rotation speed was 180.
The film was formed at rpm.

[0028]

[Table 2]

The evaluation results are shown in Table 3. The relationship between the ITO content and the surface resistance and haze value is shown in FIG.

[0030]

[Table 3] Evaluation result of transparent conductive film ━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example Surface resistance Transmittance haze value Film strength (peeling) ) (KΩ / □) (%) (%) (pencil value) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 1 47.2 96. 7 1.5 4H 2 7.62 96.2 5.4 3H 3 13.5 95.2 3.2 6H 4 1.15 93.5 5.2 3H 5 1.0 93.4 5.6 3H 6 9.7 95.1 3.3 4H 7 1.23 93.8 5.1 4H 8 4.6 94.4 4.5 6H ━━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━

In the practical range Rx of FIG. 1, the surface resistance is 5 × 10 ⁴ Ω / □ or less and the haze value is 6% or less, which shows that the characteristics as a transparent conductive film for electric field shielding are satisfied. . Further, the film strength can be improved by further adding a protective coat layer, and therefore about 3H is sufficient. Claim 1 specifies the content of the ITO fine powder within the practical range Rx.

(Example 9) ITO fine powder A in Table 1
And orthomethoxysilicate as the silicate were used to prepare a treatment liquid having the composition shown in Example 6. The film forming conditions were a substrate temperature of 36 ° C. and a rotation speed of 120 rpm.
As a characteristic of the film, a surface resistance of 1.05 × 10 ⁴ Ω / □ haze value of 3.4% was obtained.

(Example 10) A treatment liquid having the composition shown in Example 6 was prepared by using the ITO fine powder C in Table 1 and orthomethoxysilicate and orthobutoxysilicate (the ratio of methoxy and butoxy was 1: 1) as the silicate. Was prepared. The film forming conditions are a substrate temperature of 56 ° C. and a rotation speed of 15
It was carried out at 0 rpm. Surface resistance 9.4 × 10 as film characteristics
^{A 3} Ω / □ haze value of 3.6% was obtained.

Example 11 A treatment liquid having the composition shown in Example 6 was prepared by using the ITO fine powder C in Table 1 and orthopropoxysilicate as a silicate. The film forming conditions were a substrate temperature of 55 ° C. and a rotation speed of 150 rpm. As the characteristics of the film, a surface resistance of 9.7 × 10 ³ Ω / □ and a haze value of 3.8% were obtained.

From the above Examples 9 to 11, ITO fine powder A to
Whether C is used or methoxy, ethoxy, propoxy or butoxy is used as the silicate, as long as the conditions described in the claims are satisfied, the requirements for a transparent conductive film for an electric field shield are satisfied. I understand.

Comparative Example 1 ITO fine powder D in Table 1
And orthomethoxysilicate as the silicate were used to prepare a treatment liquid having the composition shown in Example 6. The film forming conditions were a substrate temperature of 50 ° C. and a rotation speed of 150 rpm.
Surface resistance 9.8 × 10 ³ Ω / □ haze value 2 as film characteristics
0.8% was obtained. Since the formed film has a high haze value, it is unsuitable as a coating film for a cathode ray tube.
The treatment liquid with the ITO fine powder D cannot be used for coating a cathode ray tube.

(Comparative Examples 2 to 7) The treatment liquids shown in Table 4 were prepared using the ITO fine powder B shown in Table 1 and orthomethoxysilicate as the silicate.

(Comparative Example 8) ITO fine powder B shown in Table 1
And orthomethoxysilicate as the silicate were used to prepare the treatment liquids shown in Table 4. However, as a preparation method, NMP was not used as a dispersion solution when applying a ball mill, and an ITO solution was prepared only with ethanol, and then added as a dilute solution together with alcohols so that the composition was the same as that of Example 6. .

For the evaluation of the comparative example, the glass substrate temperature was 40 ° C. and the spin coating rotation speed was 160 rpm to form a film.

[0040]

[Table 4]

Table 5 shows the evaluation results.

[0042]

[Table 5] Evaluation results of transparent conductive film ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Comparative example Surface resistance Transmittance Haze value Film strength (peeling) (kΩ / □) (%) (%) (pencil value) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━ 2 4.7 × 10 ⁹ 99 0.8 3H 3 7.52 93.2 12.2 There is some cracking 4 14.5 95.1 Less than 4.5 HB (no film formation) ) 5 4.5 × 10 ⁸ 95.2 4.7 9H 6 23.5 93.1 12.1 3H 7 8.3 95.2 3.0 Less than HB (with film unevenness) 8 20.2 93.0 11.5 2H ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

In Comparative Example 2, since the ITO concentration was low, the film thickness was thin and a uniform film could not be obtained. Further, since the formed film has high surface resistance, it cannot be effective as an electric field shield film. Comparative Example 3 shows an example in which the ITO concentration is high. The film formed using the treatment liquid of Comparative Example 3 became thicker and some cracks occurred. There is also a problem with the uniformity of the film. Comparative Example 4 shows an example in which the ratio of silicate to ITO is small. If the content of silicate is low, the film is hardly formed, and the film is damaged by the measuring probe when measuring the surface resistance. Comparative Example 5 shows an example in which the content of silicate in the ITO powder is large. In this case, it can be seen that the obtained film has high surface resistance and no electric field shielding effect.

Comparative Examples 6, 7 and 8 are to be compared with Example 6. Comparative Example 6 shows an example in which the NMP content is less than 1% by weight. In this case, IT
It can be seen that the dispersibility of the O fine particles is poor and the haze is high.
Comparative Example 7 shows an example in which the NMP content is 20% by weight or more. In this case, it is found that the film forming property is poor and the film strength is low. In Comparative Example 8, although the composition was the same as that of the treatment liquid shown in Example 6 of Table 2, a method for preparing the treatment liquid (ITO
This is an example when the method of dispersing particles) is changed. In this case, it can be seen that the dispersibility of ITO particles is poor and the haze is high.

[0045]

As described above, according to the present invention, the conductive particles have a tin content of 1 to 10% by weight and an average particle size of 50.
using indium tin oxide particles (ITO) of
Alkyl silicate as binder, N-methyl- as polar solvent
By selecting and using 2pyridinone, ethanol, acetone, tetrahydroquinone, etc., a low-temperature firing gives a processing liquid for electric field shielding which has a small surface resistance and enables film formation by coating, spraying or spin coating. In particular, the content of alkyl silicate is 0.1 to 6% by weight, and IT
By selecting the mixing ratio of O particles and alkyl silicate in a weight ratio of 0.1 to 0.6, a transparent conductive film having an appropriate haze value and surface resistance value can be obtained, and applied to the surface treatment of a cathode ray tube. It has an effect of effectively preventing the obstacle due to the leakage electric field.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an ITO content and a surface resistance and a haze value.

Front page continuation (72) Keiichi Orita Inventor Keiichi Orita 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo Inside Tohoku Kako Co., Ltd.

Claims (3)

[Claims] 1. A treatment liquid for electric field shield in which indium tin oxide powder and a binder are dispersed in a polar solvent, wherein the indium tin oxide powder has a tin content of 1 to 10% by weight and an average particle diameter. 50 nm or less, containing 1 to 15 wt%, the binder is an alkyl silicate whose alkyl group is methyl, ethyl, propyl, butyl, the content of alkyl silicate is 0.1 to 6 wt%, and polar. The solvent contains N-methyl-2pyrrolidinone and one or more of ethanol, acetone, tetrahydroxyfuran, isopropyl alcohol, diacetone alcohol, and dimethylformamide. liquid. 2. The treatment liquid for electric field shield according to claim 1, wherein the mixing ratio of the indium tin oxide powder and the alkyl silicate is 0.1 to 0.6 in weight ratio. 3. The polar solvent contains N-methyl-2pyrrolidinone and ethanol, the content of N-methyl-2pyrrolidinone is 1 to 20% by weight, and the content of ethanol is 25 to 90. The treatment liquid for electric field shield according to claim 1, wherein the treatment liquid is wt%.